Network Working Group J. White
Request for Comments: 524 SRI-ARC
NIC: 17140 13 June 1973
A Proposed Mail Protocol
AUTHOR'S INTENT
This is the document I offered in (15146,) to write. It's a proposed
specification for handling mail in the Network -- a Mail Protocol.
Main handling is currently implemented as two FTP commands, MAIL and
MLFL, which permit an FTP user process to deliver a file or string of
text to an FTP server process, designating it as mail to be made
available to a user, identified by a local name, in its host. The
protocol proposed here is much richer than that, both in terms of the
functions it supports, and in terms of the flexibility it provides.
Although one can (I think) and might, implement software on the basis
of this document, this REALLY IS a Request for Comments. Comments,
questions, position papers are solicited. There are, I'm sure, bugs
in the protocol specified here, and I hope that readers will point
them out via RFC as they discover them.
Various members of the Network community have, during the last few
months, pointed out to me specific inadequacies in the existing mail
commands and asked me to be conscious of them in designing a new
protocol. I've tried to do that. If anyone feels that his concern
wasn't properly dealt with here, or that it slipped through the
cracks entirely (for which I apologize in advance), I would
appreciate it if he would prod me once more.
INTRODUCTION
THE MAIL PROTOCOL ENVIRONMENT
The Mail Protocol (MP) is implemented by Mail user and server
processes, in keeping with the model for previous high-level
protocols. The Mail user and server processes are further
specified to be also FTP user and server processes, respectively.
That is, MP is implemented as a set of commands accessible from
within the FTP command space.
The MP command set is defined to lie conceptually within a
subsystem, invoked from the FTP command space with the command
MAIL .
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RFC 524 A Proposed Mail Protocol 13 June 1973
NOTE: Since a command called 'MAIL' already exists within the
FTP command space, the command name 'XMAIL' might substitute
for 'MAIL' while the current mail commands are being phased
out.
The MP command set may or may not (according to the implementation
of a particular server) be implemented by a process distinct from
that which implements FTP proper.
The following are implications of the 'subsystem' concept, of
which the reader (and implementer) must be aware:
(1) Names of MP commands are known only within the MP
subsystem. MP commands must (and should naturally) be rejected
by the server if the user process presents them outside of the
subsystem.
(2) Exit from the Mail subsystem (to the FTP command space) is
effected with and only with the command EXIT . FTP
commands must be rejected by the server if the user presents
them while inside the subsystem (i.e., before EXIT is issued).
(3) The same command name may be assigned without ambiguity to
two entirely different commands, provided that one lies within
the FTP command space and the other within MP, the two being
distinguishable by their contexts. MP and FTP therefore do not
compete for command names, and MP command names may be chosen
without regard for the environment in which the subsystem
resides.
NOTE: It so happens that there are commands DEFINED within MP
which duplicate the functions of FTP commands and bear the same
names. The effective result is that some commands are
explicitly allowed within MP. The reader will understand that
this fact is consistent with the conventions described in 1-3
above, and that no ambiguities result.
The subsystem concept (if not the name 'subsystem') is taken from
Mike Padlipsky's Unified User Level Protocol (UULP), which the
author of the present document strongly supports. The fact that
MP is accessed from FTP, rather than both FTP and MP being
accessed independently from a more general executive program, is
simply a concession to the fact that FTP is widely implemented and
UULP isn't. The author hopes that protocol development will, in
the near future, begin to proceed along the lines exemplified by
UULP.
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RFC 524 A Proposed Mail Protocol 13 June 1973
MP conforms to FTP in general syntax. In particular, commands and
their responses are strings of NVT characters; command names are
limited to four or fewer, upper- or lower-case, alphameric
characters, and are terminated by the character SP; commands are
generally terminated with the TELNET New Line sequence (CR LF);
command responses contain both numeric (process readable) and text
(human readable) portions. Both reader and implementer are
referred to the FTP protocol document for a detailed description
of such matters; no attempt has been made to duplicate the
discussion in the present document.
The FTP protocol document assigns those replies whose second digit
is '6' to RJE functions. In like manner MP appropriates those
reply codes whose second digit is '7' for reporting results
peculiar to its functions. It is, however, the author's position
that FTP, MP, and the RJE protocol are all best implemented as
subsystems under a common UULP executive, in which case a single
subset of the reply space could be used unambiguously by all three
protocols (and any yet to be defined), since every reply would
implicitly be qualified by the name of the subsystem from which it
emanates.
THE MAIL MODEL
MP defines mail to be text communicated between users (both human
and processes) in less that (but ideally approaching) real time.
The definition excludes so-called console-to-console
communication, where users exchange information at the character
or line level.
Pieces of mail are characterized by such attributes as title,
content, author, and recipient. A piece of mail may be a one- or
two-line message sent from one individual to another, a draft of a
document sent by one individual to a design group for review, a
polished, formal document sent from one group to another, a
message sent to a human user by a process (e.g., an RJE server
process might notify a user by Network Mail when his job has
completed), etc. All such forms of communication are mail and are
supported by MP.
Pieces of mail can be forwarded from one location to another
Pieces of mail can be replied to.
The identity of the author of a piece of mail can be verified,
avoiding forgery and misrepresentation.
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RFC 524 A Proposed Mail Protocol 13 June 1973
Pieces of mail can be permanently recorded, assigned a long-term
identifier by which they can be forever be retrieved for
reference, and entered in catalogs. And access to such recorded
mail can be restricted to a specified subset of the user
community.
Some hosts accept mail whose recipients reside elsewhere in the
Network, and assume responsibility for delivering the mail to them
(worrying about retrying delivery when hosts are down, etc.), and
acknowledging its delivery to the sender.
The picture being painted for the reader is one in which processes
cooperate in various ways to flexibly move and manage Network
mail. The author claims (without proof, of course) that the
picture will in the future get yet more complicated, but that the
proposal specified here can be conveniently enlarged to handle
that picture too.
ORGANIZATION OF THIS DOCUMENT
The rest of this document consists of the following components:
GLOSSARY
The concepts introduced briefly in the section above are more
formally defined, and their manner of representation in the
protocol specified.
MP FUNCTIONS
The command sequence is defined by which a user process
initiates each of the logical functions (e.g., Distribution,
Recording, Delivery) which can be performed by a Mail server
process.
EXAMPLE
An example of the command-response exchange between a user and
server is given.
COMMAND SUMMARY
A summary of MP commands is given.
COMMAND REPLIES
Reply code assignments are given and briefly explained.
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RFC 524 A Proposed Mail Protocol 13 June 1973
FORMAL SYNTAX
The formal syntax of the command language is specified.
In all sections but the last (i.e., the formal syntax presentation),
verbose keyword forms are employed, in the interests of clarity.
These verbose forms have no existence anywhere but in this document;
in implementing a Mail user or server process, the terse keyword
forms which appear in the formal syntax presentation are to be
employed
GLOSSARY
Terms are listed here in alphabetical order. Words or phrases which
appear in the definitions with initial letters capitalized are
themselves formally defined elsewhere in the glossary.
ACCESS LIST (for a piece of Recorded Mail)
That set of individuals with access to a piece of Recorded Mail,
and for each such individual, the type(s) of access granted to
him.
An Access List is represented in the Protocol as a series of
command pairs (juxtaposed in the command stream), each pair
consisting of an ACCESS command followed immediately (and
optionally) by an ACCESSTYPES command. Each pair of commands
corresponds to one individual in the set.
ACCESS
ACCESSTYPE
Command arguments identify the Individual to whom access is
granted, and specify the kind(s) of access allowed him.
Either Read Access, Controlling Access, or both may be
granted.
If no Individual is specified, All is implied. In the
absence of an explicit ACCESSTYPES command, one with only
Read Access specified is to be assumed.
In the absence of an explicit Access List, one granting Read
Access to All and Controlling Access to the Author(s) and the
Clerk is to be assumed.
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RFC 524 A Proposed Mail Protocol 13 June 1973
ACKNOWLEDGMENT (for a piece of Mail)
A form of Unrecorded Mail, generated by a Distribution Agent,
whose Recipient is the Monitor for a previous piece of Mail, which
acknowledges Delivery -- successful or otherwise -- to the
Recipient(s) of that first piece of Mail.
An Acknowledgment bears the Serial Number of the Mail it
acknowledges, as the Reference Serial Number.
ACKNOWLEDGMENT CONDITION (for Acknowledgments)
The attribute of an Acknowledgment which determines the
circumstances under which it will be generated by the Distribution
Agent.
The following Acknowledgment Conditions are defined:
ALWAYS
Acknowledgment is given when all Deliveries are complete,
regardless of whether or not they are all completed
successfully.
FAILURE
Acknowledgment is given when all Deliveries are complete if
and only if Delivery to one or more Recipient(s) fails.
NEVER
An Acknowledgment is never made.
An Acknowledgment Condition is represented in the Protocol by the
command:
ACKCONDITION
In the absence of an explicit ACKCONDITION command, one with an
argument of FAILURE is to be assumed.
ACKNOWLEDGMENT TYPE (for Acknowledgments and Progress Reports)
The attribute of an Acknowledgment or Progress Report which
determines the nature of its Content.
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The following Acknowledgment Types are defined:
TERSE
The Content of a TERSE Acknowledgment or Progress Report is
specified by the Protocol to be an unembellished list of the
Mail's Recipient(s), and the current Delivery Status for
each (except that those Recipient(s) whose Delivery Status
is SUCCESSFUL shall not be included in the list).
The Content of a TERSE Acknowledgment is one or more
instances of the following:
TERSE Acknowledgments and Progress Reports are intended to
be process-readable.
VERBOSE
The Content of a VERBOSE Acknowledgment or Progress Report
is not specified by the Protocol, but might include a list
of those Recipient(s) to whom the Mail could not be
delivered and why, the times at which Delivery was made to
others, etc.
VERBOSE Acknowledgments and Progress Reports are intended to
be human-readable.
An Acknowledgment Type is represented in the Protocol by the
command:
ACKTYPE
In the absence of an explicit ACKTYPE command, one with an
argument of TERSE is to be assumed.
ALL
Every conceivable Individual.
AUTHOR (of a piece of Mail)
An Individual (there may be more than one) given formal
recognition for having authored a piece of Mail.
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AUTHOR LIST (for a piece of Mail)
That set of Individuals who are Author(s) of a piece of Mail.
An Author List is represented in the Protocol as an Individual
List of type AUTHOR.
CATALOG (of Recorded Mail)
A named data base containing the Citation for each member of a set
of logically related pieces of Recorded Mail.
CATALOG LIST (for a Piece of Recorded Mail)
That set of Catalogs which each contain the Citation for a piece
of Recorded Mail
A Catalog List is represented in the Protocol as a series of
instances (juxtaposed in the command stream) of the following
command. Each instance corresponds to one Catalog in the set.
CATALOG
CITATION (for a piece of Recorded Mail)
The Static and Dynamic Attributes of a piece of Recorded Mail.
CITATION COMPONENT
Any one of the Static or Dynamic Attributes which comprise a
Citation.
CITATION RETRIEVAL (for a piece of Recorded Mail)
The act of retrieving selected Citation Component(s).
CITATION TEMPLATE
A specified subset of the Citation Component(s) for a piece of
Recorded Mail.
A Citation Template is represented in the Protocol by the command:
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CITATIONTEMPLATE
The argument is a list of Citation Component(s). In the absence
of an explicit CITATIONTEMPLATE command (or if the argument is
null), one specifying Content only is to be assumed.
CLERK
That Individual who prepares a piece of Mail for Recording,
Distribution, or Delivery. Conceptually, the Individual with
proof-reading responsibility for the piece of Mail.
A Clerk is represented in the Protocol as an Individual List of
type CLERK and length 1.
COMMENTS (for a piece of Mail)
An informal, perhaps verbose description of the Content of a piece
of Mail, or any other information the Author(s) wish to have made
accessible to the Recipient(s) of the Mail.
Comments are represented in the Protocol by the command:
COMMENTS
In the absence of an explicit COMMENTS command, one with a null
argument is to be assumed.
CONTENT (of a piece of Mail)
It's text.
Content is represented in the protocol by either of the two
commands below:
FILE
The FILE command implies that the Content of the Mail will
be transmitted (immediately) as a file using the FTP data
transfer commands (e.g., BYTE, SOCK, TYPE) currently in
effect. FILE is exactly equivalent in use to an FTP STOR
command (in its use of data transfer commands, in its
establishment of the data connection, etc.), except that no
pathname is required, and the server, rather than depositing
the transmitted file in his file system, disposes of it in a
manner appropriate for Mail.
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TEXT
The TEXT command implies that the Content of the Mail
follows on the TELNET connection as a series of lines, each
delimited from the preceding one by CR LF, and terminated
finally by a CA2.
CONTROLLING ACCESS (to a piece of Recorded Mail)
The right of an Individual to modify a Dynamic Attribute of a
piece of Recorded Mail.
Recording Agents permit an Individual to modify a Dynamic
Attribute of a piece of Recorded Mail if and only if he can
properly identify himself as someone having Controlling Access to
that Mail.
CREATION DATE (of a piece of Mail)
The date and time at which the final draft of a piece of Mail is
completed by the Clerk before he releases it to a Delivery,
Distribution, or Recording Agent for further processing. A single
Creation Date is associated with each piece of Mail. In general,
this date is different from the Delivery or Recording Date, since
Mail often must be queued (for another host to come up) within the
Delivery, Distribution, or Recording Agent's host before Delivery
of Recording can occur.
A Creation Date is represented in the Protocol by the command:
CREATIONDATE
CUTOFF INTERVAL (for Distribution of a piece of Mail)
That period of time, measured from the Distribution Date, after
which the Distribution Agent is to abandon Delivery attempts for
those Recipient(s) to whom Delivery has not yet been effected.
A Cutoff Interval is represented in the Protocol by the command:
CUTOFF
In the absence of an explicit CUTOFF command, one specifying an
Interval of 7 days is to be assumed.
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DELIVERY (of a piece of Mail)
The act of transmitting a piece of Mail to the host of one of it's
Recipient(s).
DELIVERY AGENT
A process which effects Delivery of a piece of Mail. A
Distribution Agent is by nature also a Delivery Agent.
DELIVERY DATE (of a piece of Mail to one of its Recipient(s))
The date and time at which a piece of Mail is Delivered by the
Delivery Agent to a Recipient's system. A multitude of Delivery
Dates, one for each Recipient, are associated with each piece of
Mail.
DELIVERY STATUS (for a piece of Mail with respect to a Recipient)
A measure of the extent to which a Delivery Agent has been
successful, at a given point in time, in Delivering a piece of
Mail to one of its Recipient(s). A multitude of Delivery Status',
one for each Recipient, are associated with each piece of Mail.
The following Delivery Status' are defined:
FAILED
Delivery was rejected by the Recipient's system (e.g., the
connection request was rejected, the Mail server process
doesn't support Delivery, the Recipient was not recognized
by the server).
SUCCESSFUL
Delivery was accomplished successfully.
TIMED OUT
Either the Recipient's host was disconnected from the Net at
every Delivery attempt, or no Mail server process has ever
responded to the connection attempt. Hope of Delivery has
been abandoned.
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WAITING
Either the Recipient's host has been disconnected from the
Net at every Delivery attempt, or no Mail server process has
yet responded to the connection attempt. Delivery attempts
are continuing periodically.
UNATTEMPTED
No delivery attempt has yet been made.
DELIVERY TYPE (for a Delivery)
The nature of the piece of Mail being delivered.
The following Delivery Types are defined:
FORWARD
A Delivery of type FORWARD represents a piece of Recorded or
Unrecorded Mail which is being Forwarded.
MAIL
A Delivery of type MAIL represents a piece of Recorded or
Unrecorded Mail whose ultimate source is an Individual.
This is the "normal" Delivery type.
NEGATIVE ACKNOWLEDGMENT
A Delivery of type NEGATIVE ACKNOWLEDGMENT represents a
piece of Unrecorded Mail generated by a Distribution Agent
and acknowledging unsuccessful or partially unsuccessful
Delivery of a previous piece of Mail (identified by
Reference Serial Number) to it's Recipient(s). The
Recipient for this piece of "system" Mail is the Monitor for
the previous piece of Mail.
POSITIVE ACKNOWLEDGMENT
A Delivery of type POSITIVE ACKNOWLEDGMENT represents a
piece of Unrecorded Mail generated by a Distribution Agent
and acknowledging successful Delivery of a previous piece of
Mail (identified by Reference Serial Number) to it's
Recipient(s). The Recipient for this piece of "system" Mail
is the Monitor for the previous piece of Mail.
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PROGRESS REPORT
A Delivery of type PROGRESS REPORT represents a piece of
Unrecorded Mail generated by a Distribution Agent and
reporting the Delivery of a previous piece of Mail
(identified by Reference Serial Number) to it's
recipient(s). The Recipient for this piece of "system" Mail
is the Monitor for the previous piece of Mail.
REPLY
A Delivery of type REPLY represents a piece of Recorded or
Unrecorded Mail generated in reply (or pertaining) to a
previous piece of Mail (identified by Reference Serial
Number).
Delivery Type is represented in the Protocol by the command:
DELIVERYTYPE
In the absence of an explicit DELIVERYTYPE command, one with
argument of MAIL is to be assumed.
DISTRIBUTE DATE (for a piece of Mail)
The date and time at which a piece of Mail is presented to a
Distribution Agent for Distribution.
DISTRIBUTION (of a piece of Mail)
The act of Delivering a piece of Mail to its Recipient(s).
Distribution can be effected by either the Clerk's Delivery Agent,
or by a Distribution Agent acting on his behalf.
DISTRIBUTION AGENT
A Mail server process which acts as intermediary in the delivery
process by accepting Mail for Recipient(s) in hosts other than its
own, and then assuming responsibility for Delivering the Mail to
them and returning Acknowledgment to the appointed Monitor.
DISTRIBUTION LIST
In the Delivery or Distribution of a piece of Mail, that set of
Individuals who are to receive Delivery of the Mail.
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In the Recording of Mail, that set of Individuals who have
received formal and authorized Delivery of a piece of Mail. The
list is kept current by Distribution Agents. Of course, any
Individual with Read Access to the Mail can himself Deliver it
informally to anyone he chooses without that fact's being
reflected in the Distribution list.
A Distribution List is represented in the Protocol as a series of
command quintuplets (juxtaposed in the command stream), each
quintuplet consisting of a RECIPIENT command, followed immediately
(and optionally) by any or all of the following in the order
given: a GENERALDELIVERY, a GREETING, a SIGNATURE, and a
DISPOSITION command.
Each quintuplet corresponds to one individual in the set.
RECIPIENT
GENERALDELIVERY
This command is appropriate only in the context of the
Delivery function. If the previous RECIPIENT command
illicits the reply:
474 Recipient unrecognized: is General Delivery
OK?
the issuance of the GENERALDELIVERY command constitutes
consent to proceed with General Delivery to that Recipient.
If no such consent is given, the RECIPIENT command stands
rejected. Unsolicited (i.e., unprompted for) GENERAL
DELIVERY commands in the Distribution List are treated by
the server as NOPs.
GREETING
The GREETING command specifies the Greeting to be seen by
the Recipient.
If the first quintuplet in the list contains no GREETING
command, one with a null argument is assumed. Thereafter,
in the absence of an explicit GREETING command, one
identical to that for the previous quintuplet is assumed.
SIGNATURE
The SIGNATURE command specifies the Signature to be seen by
the Recipient.
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If the first quintuplet in the list contains no SIGNATURE
command, one with a null argument is assumed. Thereafter,
in the absence of an explicit SIGNATURE command, one
identical to that for the previous quintuplet is assumed.
DISPOSITION
The DISPOSITION command identifies the intent with which the
Mail is Delivered to the Recipient by the Author(s), and may
take any, all, or none of the following as arguments:
RSVP
The Author(s) request a Reply from the Recipient.
ACTION
The Author(s) expect some action on the part of the
Recipient. If ACTION doesn't appear, then the Mail is
intended for the Recipient's information only.
INTERRUPT
The Author(s) declare that examination of the Mail by
the Recipient is urgent. In such cases, the
Recipient's Mail server process may, upon Delivery,
choose to interrupt the Recipient if he happens to be
logged in at a terminal.
No specific action in response to the presence of any of
these arguments is required; the server is free if he likes
to treat DISPOSITION commands as NOPs.
The absence of a DISPOSITION command implies one with no
arguments (i.e., for the Recipient's information only, no
Reply required, and not urgent).
DYNAMIC ATTRIBUTES (of a piece of Recorded Mail)
Those attributes of a piece of Recorded Mail -- Distribution List,
Access List, and Catalog List -- which, though given initial
values at Recording Time, can always be modified by an Individual
with Controlling Access to the piece of Mail.
FORWARDING (of Mail received for an Individual)
The act of transferring that set of Mail which has been previously
Delivered to but not Read by an Individual, to another Individual.
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Users who are known at more than one host can cause their unRead
Mailto be gathered in to a central location by performing the
Forwarding function at each such host (both Individuals being, in
this case, instances of the same User). Mail which has been
Forwarded is considered to have been Read at its source.
FORWARDEE
That Individual whose Delivered but UnRead Mail is to be
Forwarded.
A Forwardee is represented in the Protocol as an Individual List
of type FORWARDEE and length 1.
GENERAL DELIVERY (of a piece of Mail to an unrecognized Recipient)
The act on the part of a server of accepting Delivery of a piece
of Mail on behalf of an intended Recipient whose name the server
doesn't recognize. The server retains the Recipient's name, and
makes it and the other information provided by the user process
available to some competent person, who attempts to make sense of
the Recipient's name. If the Recipient is recognized, the Mail is
'hand' delivered to the appropriate Individual.
General Delivery of a piece of Mail to one of its intended
Recipient(s) is performed only after the server informs the user
process of its intent and receives the user process' consent. If
that consent is not given, or if the server doesn't implement
General Delivery, the server rejects the Delivery attempt for that
Recipient.
Consent for General Delivery is represented in the Protocol by the
command
GENERALDELIVERY
GREETING (for the Delivery of a piece of Mail to a Recipient)
A short greeting to a Recipient of a piece of Mail. 'Dear Dave' is
a valid and perhaps typical Greeting.
A Greeting is represented in the Protocol by the command:
GREETING
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ID (for an Individual)
The password which an Individual may have to present to a Mail
server process, to prove his identity.
An Id is represented in the Protocol by the command:
ID
Ids have nothing to do with accounting, and when required by a
server, they're required only to protect that server from forgery
or misrepresentation.
INDIVIDUAL
An instance of a User, identified by NIC Ident, or by the
combination of host and Mailbox Name.
INDIVIDUAL LIST (of type "t" and length "n")
A set of Individuals.
An Individual List is represented in the Protocol as a series of
"n" command pairs (juxtaposed in the command stream), each pair
consisting of a "t" command, followed immediately by an ID
command. Each pair corresponds to one Individual in the set.
The ID command is given by the Mail user process at the option of
the Mail server process; and whenever the server requires it, he
must prompt for it with an appropriate reply to the preceding "t"
command. If no such prompt is given, the user process is not
obliged to provide the ID command, but may if it chooses, in which
case the server is obliged to treat it as if it had been prompted
for and found correct.
The ID command is a mechanism by which the server can assure
himself that the user process is not acting without proper
authorization from the Individual(s) involved, i.e., a mechanism
by which a server can protect himself against forgery,
misrepresentation, etc.
"t"
ID
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MAIL
A body of text communicated from one set of Individual(s) to
another, in less than (but ideally approaching) real time.
MAILBOX NAME
The name a User employs at a host to send and receive Mail.
MONITOR (for a piece of Mail)
The Individual who is the recipient for Acknowledgments and
Progress Reports.
A Monitor is represented in the Protocol as an Individual List of
type MONITOR and length 1.
Monitor defaults to the Clerk if not explicitly specified.
PROGRESS REPORT (for a piece of Mail)
A form of Unrecorded Mail, generated periodically during the
distribution process by a Distribution Agent, whose Recipient is
the Monitor for a previous piece of Mail, and whose Content is a
list of the Recipient(s) and the current Delivery Status for each.
A Progress Report bears the Serial Number of the Mail whose status
it reports, as the Reference Serial Number.
PROTOCOL
The Mail Protocol (MP).
READ (a piece of previously-Delivered Mail)
The act, on the part of the User, of examining a piece of
Delivered Mail.
READ ACCESS (to a piece of Recorded Mail)
The right of an Individual to retrieve the Content of a piece of
Recorded Mail.
Recording Agents permit an Individual to retrieve the Content of a
piece of Recorded Mail if and only if he can properly identify
himself as someone having Read Access to that Mail. An Individual
can retrieve the Citation (except Content) from the Recording
Agent independently of whether or not he has Read Access to the
Mail.
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READ DATE (of a piece of Mail for one of its Recipient(s))
The date and time, necessarily following Delivery, at which a
piece of Mail is Read by a Recipient. A multitude of Read Dates,
one for each Recipient, are associated with each piece of Mail.
RECIPIENT (of a piece of Mail)
An Individual who has or is to receive Delivery of a piece of
Mail.
RECORDED MAIL
A piece of Mail whose Citation is available on a long-term
(indefinite) basis from a Recording Agent.
RECORDING
The service provided by a Recording Agent.
RECORDING AGENT
A Mail server process which accepts Mail, permanently Records its
Citation, and assigns a pathname by which that information can at
any time be retrieved by an Individual with appropriate access.
RECORDING DATE
The date and time at which a piece of Mail is presented to a
Recording Agent for Recording. A single Recording Date is
associated with each piece of Recorded Mail.
REFERENCE SERIAL NUMBER (for an Acknowledgment, Progress Report, or
Reply)
The Serial Number of the piece of Mail to which an Acknowledgment,
Progress Report, or Reply refers.
A Reference Serial Number is represented in the protocol by the
command:
REFERENCESERIAL
In the absence of an explicit REFERENCESERIAL command, no Serial
Number is to be assumed.
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REPLY (to a previous piece of Mail)
A piece of Recorded or Unrecorded Mail whose Author(s) are
Recipient(s) of a previous piece of Mail, and which replies or
pertains to that same piece of Mail and bears its Serial Number,
as the Reference Serial Number.
REPORT INTERVAL (for a Progress Report)
The interval between Progress Reports.
A Report Interval is represented in the Protocol by the command:
REPORTINTERVAL
In the absence of an explicit REPORTINTERVAL command, one with an
argument whose value is effectively infinite is to be assumed
(i.e., no Progress Reports are to be made).
REQUESTOR
The Individual on whose behalf a Mail user process connects to and
interacts with a Mail server process.
A Requestor is represented in the Protocol as an Individual List
of type REQUESTOR and length 1.
SERIAL NUMBER (for a piece of Mail)
A short-term identifier, assigned to a piece of Mail by the Clerk
(or his system), which accompanies Acknowledgments, Progress
Reports, and Replies, and is used to correlate the latter with the
former. The lifetime of a Serial Number is conceptually from its
assignment by the Clerk until the Delivery of the Recipient(s)
Reply(s) to the Author(s) (or until their decision to send no
reply).
A serial Number is represented in the Protocol by the command:
SERIAL
In the absence of an explicit SERIAL command, no Serial Number is
to be assumed.
SIGNATURE (for the delivery of a piece of Mail to a Recipient)
A human-readable indication of the Author(s) of a piece of Mail.
The string 'Jim and Dick' is a valid Signature.
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RFC 524 A Proposed Mail Protocol 13 June 1973
A Signature is represented in the Protocol by the command:
SIGNATURE
STATIC ATTRIBUTES (of a piece of Recorded Mail)
Those attributes of a piece of Recorded Mail -- Content, Title,
Comments, Author(s), Clerk, and Creation Date -- which are forever
fixed at Recording Time, and hence can never be modified.
Static Attributes can be independently specified with commands
described elsewhere, or specified collectively by reference to an
existing piece of Recorded Mail. The command which follows
assigns to the current piece of Mail the Static Attributes of the
piece of Recorded Mail it references, and is exactly equivalent to
an appropriate set of TITLE, COMMENTS, etc. commands.
LOCATION
TITLE (of a piece of Mail)
A concise description of the Content of a piece of Mail.
A Title is represented in the Protocol by the command:
TITLE
In the absence of an explicit TITLE command, one with a null
argument is to be assumed.
UNRECORDED MAIL
Mail which is never presented to a Recording Agent for permanent
storage and cataloging, but which is simply Delivered to its
Recipient(s) by a Delivery Agent.
UPDATE REQUEST (to a Recording Agent for a piece of Recorded Mail)
A request made of a Recording Agent to add, replace, or delete an
Individual from the Access or Distribution List for a piece of
Mail; or to add or delete a Catalog from the Catalog List.
An Update Request is represented in the Protocol by the command:
UPDATETYPE
followed immediately in the command stream by an Access,
Distribution or Catalog List.
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RFC 524 A Proposed Mail Protocol 13 June 1973
USER
A process or human who sends and/or receives Mail.
USER VERIFICATION
The act of verifying an ID as that of a specified Individual.
USER VERIFICATION AGENT
A Mail server process which performs User Verification
MP FUNCTIONS
A MP function is the request by a Mail user process and the
subsequent performance by a server, of a major task related to the
management of Mail. The following functions are defined:
RECORDING
DELIVERY
DISTRIBUTION
FORWARDING
CITATION RETRIEVAL
UPDATE CITATION
USER VERIFICATION
One might expect that within the Network there would be just a few
Recording Agents (who implement the Recording, Citation Retrieval,
and Update Citation functions); a few Distribution Agents (who
implement the Distribution function); one or two User Verification
Agents (who implement the User Verification Function); and many hosts
who implement the Delivery and Forwarding functions.
In general, a host is free to implement any, all, or none of the
functions defined by the Protocol; and a host is free to require a
login (for purposes of accounting) before permitting a user process
access to any of the function(s) it has implemented.
An FTP server process who chooses to not implement MP or a particular
MP function simply rejects the command that requests the
unimplemented server with the reply:
400 Function not implemented.
A server who chooses to require login before allowing access to the
MP subsystem or to an MP function, simply rejects the command that
requests the charged-for service with the reply:
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RFC 524 A Proposed Mail Protocol 13 June 1973
332 Login first, please.
The functions defined in MP are:
RECORDING
The Recording function is invoked with the command:
RECORD
Once this command is given, the user process shall provide the
following (in any order that suits it):
(1) Any Static Attributes desired.
Content and Clerk are required. Defaults for other
Static Attributes (applied by the server if the
appropriate commands don't appear) are as follows:
Title or Comments as specified in the glossary.
Author to the Clerk.
Creation Date to the Recording Date.
(2) Initial values for any Dynamic Attributes desired.
Defaults (applied by the server if the appropriate
commands don't appear) are as follows:
Distribution and Catalog Lists to null.
Access List as specified in the glossary.
The Recording function is terminated with either of the
commands:
EXIT or ABORT
EXIT represents normal termination, and causes the server to
perform the Recording function for which parameters have just
been given. ABORT represents abnormal termination and effects
exit from the function with no action having been taken by the
server; the whole command exchange, beginning with RECORD, is
therefore a NOP.
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RFC 524 A Proposed Mail Protocol 13 June 1973
DELIVERY
The Delivery function is invoked with the command:
DELIVER
Once this command is given, the user process shall provide the
following (in any order that suits it):
(1) Any Static Attributes desired.
Content is required. Defaults for other Static
Attributes (applied by the server if the appropriate
commands don't appear) are as follows:
Title or Comments as specified in the glossary.
Clerk to null
Author to the Clerk.
Creation Date to the Delivery Date.
(2) Any Dynamic Attributes desired.
Distribution List is required. Defaults (applied by the
server if the appropriate commands don't appear) are as
follows:
Catalog List to null
Access List as specified in the glossary.
Both of these attributes are for the Recipient's
information only when presented in the context of
Delivery, so defaulting them to null simply implies
that the Clerk doesn't desire that they be
communicated to the Recipient.
(3) Any or all of the following optional parameters:
(a) Delivery Type
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RFC 524 A Proposed Mail Protocol 13 June 1973
(b) Acknowledgment Type
The specification of this parameter is appropriate if
and only if the Delivery Type is POSITIVE or NEGATIVE
ACKNOWLEDGMENT or PROGRESS REPORT. In this context,
Acknowledgment Type tells the server how to interpret
the Content of the Acknowledgment.
(c) Serial Number
The Serial Number assigned to the piece of Mail being
Delivered. This parameter is inappropriate unless the
Delivery type is FORWARD (in which case the Serial
Number is the one preserved from the previous
Delivery), MAIL, or REPLY.
(d) Reference Serial Number
The Serial Number assigned to the piece of Mail to
which the current piece of Mail is either an
Acknowledgment, Progress Report, or Reply. The
specification of this parameter is therefore
inappropriate if the Delivery Type is MAIL.
The Delivery function is terminated with either of the
commands:
EXIT or ABORT
EXIT represents normal termination, and causes the server to
perform the Delivery function for which parameters have just
been given. ABORT represents abnormal termination and effects
exit from the function with no action having been taken by the
server; the whole command exchange, beginning with DELIVER, is
therefore a NOP.
DISTRIBUTION
The Distribution function is invoked with the command:
DISTRIBUTE
Once this command is given, the user process shall provide the
following (in any order that suits it):
(1) Any Static Attributes desired.
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RFC 524 A Proposed Mail Protocol 13 June 1973
Content is required. Defaults for other Static
Attributes (applied by the server if the appropriate
commands don't appear) are as follows:
Title or Comments as specified in the glossary.
Clerk to null
Author to the Clerk.
Creation Date to the Delivery Date.
(2) Any Dynamic Attributes desired.
Distribution List is required. Defaults (applied by the
server if the appropriate commands don't appear) are as
follows:
Catalog List to null
Access List as specified in the glossary.
Both of these attributes are for the Recipient(s)
information only when presented in the context of
Distribution, so defaulting them to null simply
implies that the Clerk doesn't desire that they be
communicated to the Recipient(s).
(3) Any or all of the following optional parameters:
(a) Delivery Type
MAIL, FORWARD, or REPLY only.
(b) Serial Number
The Serial Number of the Mail being Distributed.
The Distribution Agent will relay this Serial
Number to each Recipient at Delivery.
(c) Reference Serial Number
The Serial Number of the piece of Mail to which the
current piece of Mail is a Reply. The Distribution
Agent will relay this Serial Number to each
Recipient at Delivery. The specification of this
parameter is appropriate if and only if the
Delivery Type is REPLY.
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RFC 524 A Proposed Mail Protocol 13 June 1973
(d) Acknowledgment Condition
An Acknowledgment is requested from the
Distribution Agent if and only if the
Acknowledgment Condition is other than NEVER.
(e) Acknowledgment Type
(f) Cutoff Interval
(g) Report Interval
Progress Reports are requested from the
Distribution Agent if and only if this parameter is
specified explicitly.
(h) Monitor
This parameter is ignored unless either an
Acknowledgment or Progress Reports (or both) are
requested.
The Distribution function is terminated with either of the
commands:
EXIT or ABORT
EXIT represents normal termination, and causes the server to
perform the Distribution function for which parameters have
just been given. ABORT represents abnormal termination and
effects exit from the function with no action having been
taken by the server; the whole command exchange, beginning
with DISTRIBUTE, is therefore a NOP.
FORWARDING
The Forwarding function is invoked with the command:
FORWARD
Once this command is given, the user process shall provide the
following (in any order that suits it):
(1) Forwardee
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RFC 524 A Proposed Mail Protocol 13 June 1973
(2) Distribution list
This is the set of Individual(s) to whom the Mail is to
be Forwarded.
The Forwarding function is terminated with either of the
commands:
EXIT or ABORT
EXIT represents normal termination, and causes the server to
perform the Forwarding function for which parameters have just
been given. ABORT represents abnormal termination and effects
exit from the function with no action having been taken by the
server; the whole command exchange, beginning with FORWARD, is
therefore a NOP.
CITATION RETRIEVAL
The Citation Retrieval function is invoked with the command:
RETRIEVE
Once this command is given, the user process shall provide the
following (in any order that suits it):
(1) The pathname of the piece of Mail whose Citation is to
be retrieved:
PATHNAME
(2) Any or all of the following optional parameters:
(a) Citation Template
(b) Requestor
This parameter is required if and only if Content is
requested and Read Access happens not to be granted to
All, in which case the server verifies that the
Requestor has Read Access to the piece of Mail.
(c) FILE
This command is appropriate if and only if Content is
requested. The presence of this command implies that
the Content of the Mail is to be returned to the user
process (following the return on the TELNET connection
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RFC 524 A Proposed Mail Protocol 13 June 1973
of any other Citation Component(s) requested) as a
file using the FTP data transfer commands (e.g., BYTE,
SOCK, TYPE) currently in effect. FILE is exactly
equivalent in effect to an FTP RETR command (in its
use of data transfer commands, in its establishment of
the data connection etc.) except that no pathname is
required.
In the absence of a FILE command, Content is returned
on the TELNET connection like any other Citation
Component.
The server returns the Citation Components in the
order requested by the user process (except that
Content, if requested as a file, is always returned
after the 'end of citation' indication), each as a
reply whose numeric code is 172 and whose text is
exactly the command normally used to communicate that
same parameter to the server. A reply whose numeric
code is 173 terminates the reply list.
Title and Content, which (in general) may each contain
the TELNET New Line sequence (CR LF), are represented
as continued replies, using the FTP reply continuation
convention (see the FTP protocol document). The first
four characters of each reply line except the first
and last are blanks inserted by the server which must
be deleted by the user process to correctly recover
the value of the Title or Content.
The Citation Retrieval function is terminated with either of
the commands:
EXIT or ABORT
EXIT represents normal termination, and causes the server to
perform the Citation Retrieval function for which parameters
have just been given. ABORT represents abnormal termination
and effects exit from the function with no action having been
taken by the server; the whole command exchange, beginning with
RETRIEVE, is therefore a NOP.
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RFC 524 A Proposed Mail Protocol 13 June 1973
UPDATE CITATION
The Update Citation function is invoked with the command:
UPDATE
Once this command is given, the user process shall provide the
following (in any order that suits it):
(1) Requestor
This parameter is required unless Controlling Access has
been granted to All, in which case it is treated as a NOP
if given. The server verifies that the Requestor has
Controlling Access to the piece of Mail.
(2) One or more Update Requests
The Update Citation function is terminated with either of the
commands:
EXIT or ABORT
EXIT represents normal termination, and causes the server to
perform the Update Citation function for which parameters have
just been given. ABORT represents abnormal termination and
effects exit from the function with no action having been taken
by the server; the whole command exchange, beginning with
UPDATE, is therefore a NOP.
USER VERIFICATION
The User Verification function is invoked with the command:
VERIFY
Once this command is given, the user process shall specify
any number of Requestors.
The server prompts for the Id for each, the user process
provides it, and the server returns a reply whose numeric
code is 272 is the Id is correct or 472 otherwise.
The User Verification function is terminated with either of the
commands:
EXIT or ABORT
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RFC 524 A Proposed Mail Protocol 13 June 1973
EXAMPLE
In the example below, a short message is recorded for public access,
and distributed to a single recipient. The user process is assumed
already connected to the server.
Note: This would be the implementation of NIC Journal Submission,
where the NIC is understood to be both a Recording and
Distribution Agent.
Replies from the server are in brackets.
MAIL
The Mail system is invoked.
[261 RE DE DI FW CI UP UV -- supported.]
REC
The Recording function is invoked.
[200 OK.]
TITL SMFS Runs on TENEX 1.31 at the NIC
A Title is given
[200 OK.]
TEXT The NIC came up on TENEX 1.31 on 1-APR. I tried SMFS
here on the new monitor and it works fine. I don't
understand why I had problems running your copy of the code
at BBN-TENEX. Are you still unable to reference the
same archived file from two different TENEXs?
The Content of the message is entered.
[200 OK.]
CLER WHITE@SRI-ARC
The Clerk is identified as White at SRI-ARC.
[330 OK. Now Id, please]
ID id
His Id is supplied.
[200 OK.]
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RFC 524 A Proposed Mail Protocol 13 June 1973
EXIT
Exit from the Recording function is effected, and the pathname
'15490' is returned by the Recording Agent for the now Recorded
Mail.
[270 15490 -- is assigned as the pathname.]
DIST
The Distribution function is invoked.
[200 OK.]
LOC SRI-ARC 15490
The message just recorded is specified for Distribution.
[200 OK.]
RECI * DHC
The Recipient is specified via NIC Ident to be Dave Crocker at
UCLA-NMC.
[200 OK.]
GREE Dave
A Greeting is given.
[200 OK.]
DISP R
A reply is requested.
[200 OK.]
SIGN Jim
The message is signed.
[200 OK.]
ACKC A
Acknowledgment of the Mail's Delivery is requested whether
Delivery succeeds or fails..
[200 OK.]
ACKT T
The Acknowledgment is to be terse.
[200 OK.]
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RFC 524 A Proposed Mail Protocol 13 June 1973
CUT 1 D
If Delivery hasn't been effected within 24 hours, the attempt
is to be abandoned (and an Acknowledgment of failure returned).
The Monitor (to whom the Acknowledgment is sent) is allowed to
default to the Clerk.
[200 OK.]
SERI serial
A Serial Number is assigned for purposes of coordinating
Acknowledgment and Reply. A desirable implementation of the
sender's user and server processes is one in which the Serial
Number is assigned by the user process, rather than by the
human user himself in such a way that his server process can
automatically make the association between original Mail, and
subsequent Acknowledgment and Reply.
[200 OK.]
EXIT
Exit from the Distribution function is effected.
[200 OK.]
EXIT
Exit from the Mail subsystem is effected.
[200 OK.]
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RFC 524 A Proposed Mail Protocol 13 June 1973
COMMAND SUMMARY
Every command requires at least one reply from the server.
THOSE SPECIFIC TO MP
ABORT
ACCESS
ACCESSTYPES
ACKCONDITION
ACKTYPE
AUTHOR
CATALOG
CITATIONTEMPLATE
CLERK
COMMENTS
CREATIONDATE
CUTOFF
DELIVER
DELIVERYTYPE
DISPOSITION
DISTRIBUTE
EXIT
FILE
FORWARD
FORWARDEE
GENERALDELIVERY
GREETING
ID
LOCATION
MAIL
MONITOR
PATHNAME
RECIPIENT
RECORD
REFERENCESERIAL
REPORTINTERVAL
REQUESTOR
RETRIEVE
SERIAL
SIGNATURE
TEXT
TITLE
UPDATE
UPDATETYPE
VERIFY
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RFC 524 A Proposed Mail Protocol 13 June 1973
THOSE BORROWED FROM FTP
The following commands borrowed from FTP are defined (also) as MP
commands to support the transfer of the Content of a piece of Mail
in 'file' form. The reader is referred to the FTP protocol
document for a description of their use and syntax. The borrowed
commands are:
BYTE, SOCK, PASV, TYPE, STRU, MODE, REST, and SITE.
The following commands borrowed from FTP are defined (also) as MP
commands to permit changes of accounting parameters within the MP
subsystem. The accounting parameters in force when the subsystem
is entered apply (if necessary) within the subsystem until
changed. Values to which the parameters may have been changed
while in the subsystem continue in effect upon return to the FTP
command space. The borrowed commands are:
USER, PASS, and ACCT.
The following miscellaneous commands borrowed from FTP are defined
also as MP commands:
HELP and NOOP.
COMMAND REPLIES
This list is undoubtedly incomplete; some crucial reply code
assignments may be missing despite the author's attempt to foresee
the kinds of interaction that might arise between user and server and
the responses from the server that they would require.
172
In response to the EXIT command which terminates the Citation
Retrieval function.
173 End of citation.
Following a list of 172 replies.
200 OK.
This is the standard, positive acknowledgment used throughout
the Protocol.
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RFC 524 A Proposed Mail Protocol 13 June 1973
270 -- is assigned as the pathname.
In response to the EXIT command which terminates the Record
function.
271 -- supported.
In response to the MAIL command by which the user process
gains entry to the Mail subsystem. This response is
mandatory, and from it the user process can quickly determine
what function(s) are supported by the server.
272 Requestor is who he says he is.
In response to an ID command in the User Verification
function. This reply informs the user process that the Id
given is in fact that of the Individual specified.
330 OK. Now Id, please.
In response to the first command in each pair of commands in
an Individual List. This reply requires the next command from
the user process to be ID.
332 Login first, please.
In response to any command which invokes a Mail function
(e.g., RECORD, DISTRIBUTE, DELIVER), or to the MAIL command
itself. This reply implies that the requested function is
supported by the server, but that the user is required to
login before invoking it.
400 Function not implemented.
In response to any command which invokes a Mail function
(e.g., RECORD, DISTRIBUTE, DELIVER), or to the MAIL command
itself. This reply implies that the requested function is not
supported by the server.
431 Incorrect Id.
In response to the ID command in an Individual List command
pair. This reply implies that the Id specified was incorrect.
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RFC 524 A Proposed Mail Protocol 13 June 1973
440
In response to the LOCATION command. This reply implies that
the server attempted to retrieve the specified piece of Mail
from an FTP server but failed because it returned the error
reply whose text is duplicated in the current reply.
470 No such pathname.
In response to the PATHNAME command (in the Citation Retrieval
function). This reply implies that the specified pathname is
not recognized by the server.
471 No unRead Mail to Forward.
In response to the EXIT command which terminates the
Forwarding Function.
472 Requestor is NOT who he says he is.
In response to an ID command in the User Verification
function. This reply informs the user process that the Id
given is NOT that of the Individual specified.
473 You don't have Read Access to the Mail.
In response to the LOCATION command, or to the PATHNAME
command in a Citation Retrieval function. This reply implies
that the Requestor doesn't have Read Access to the piece of
Mail.
474 Recipient unrecognized; is General Delivery OK?
In response to an instance of the RECIPIENT command in a
Distribution List (in the context of the Delivery function).
This response implies that the Recipient in unrecognized, but
that the server will attempt General Delivery to him if the
user process responds with a GENERALDELIVERY command;
otherwise the Recipient is rejected.
475 That Individual is not at this host.
570 No such NIC Ident or Mailbox Name.
In response to any command in which a NIC Ident or Mailbox
Name appears as an argument. This reply implies that the
Individual specified does not exist.
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RFC 524 A Proposed Mail Protocol 13 June 1973
571 Invalid host.
In response to any command in which a host address or standard
host name appears as an argument. This reply implies that no
such host exists.
572 No such catalog.
In response to the CATALOG command. This reply implies that
no such Catalog exists.
Any '500' reply.
Any of the error replies associated with FTP RETR/STOR commands.
FORMAL SYNTAX
The terse keyword forms to be employed in actually implementing a
Mail user or server process are generated by deleting character(s)
from the corresponding verbose forms. Those deleted characters are
included but enclosed in brackets throughout the description which
follows. Spaces can be used freely between terminal elements of the
syntax, and in some cases, at least one space must separate two
elements whose boundary could not otherwise be distinguished.
::= TELNET Go Ahead character
::= TELNET new line (CR LF)
::= CR LF
::= ::= A[LWAYS] | F[AILURE] | N[EVER]
::= T[ERSE] | V[ERBOSE]
::= A[CTION] | null
::= ::= D[ISTRIBUTION]L[IST] | A[CESS]L[IST] |
C[ATALOG]L[IST] | C[ON]T[ENT] | T[ITLE] |
C[OM]M[ENTS] | AU[THOR] | CL[ERK] |
C[REATION]D[ATE]
::= | ::= | ::= ::= C[ONTROLLING] | null
::= decimal integer
::= / / ::= ::= decimal integer, 1-31
::= D[AYS]
::= F[AILED] | S[UCCESSFUL] | T[IMED OUT] |
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RFC 524 A Proposed Mail Protocol 13 June 1973
W[AITING] | U[NATTEMPTED]
::= F[ORWARD] | M[AIL] | N[EGATIVE
ACKNOWLEDGMENT] | P[OSITIVE
ACKNOWLEDGMENT] | P[ROGRESS]R[EPORT]
| R[EPLY]
::= ::= ::= | ::= RE[CORDING] | DE[LIVERY] | DI[STRIBUTION] |
F[OR]W[ARDING] | CI[TATION RETEiEVAL] |
UP[DATE] | U[SER]V[ERIFICATION]
::= * ::= ::= | ::= decimal integer, 0-255
::= standard host name
::= decimal integer, 0-23
::= H[OURS]
::= | ::= I[NTERRUPT] | null
::= | | ::= @ | @
NOTE: Host defaults to that of the server
::= COM[MENTS]